Scientists now believe there's a supermassive black hole at the center of our galaxy. But back in the day, we dreamed the galactic center held God's home planet. Or a super-civilization. What else did science-fiction authors think we'd find there?

A super matter transmitter:

In the Perry Rhodan books, Rhodan discovers a gigantic matter transmitter, "in the form of six stars arranged in a circle in the center of the Galaxy. The transmitter then sends him to the Andromeda Galaxy, 2.4 million lightyears away."

A super-powered object, with a Douglas Adams in-joke:

In the video game Spore, you can reach the center of the galaxy — assuming you can get past the machine race, the Grox — and this gives you access to the Staff Of Life, otherwise known as the Genesis Device, which is limited to just 42 uses. Any planet you use it on is instantly terraformed, much like the Genesis Device in Star Trek.

The Empire Star, a point where space and time are multiplex.

In Empire Star by Samuel Delany, Jo is entrusted to carry a message to the Empire Star at the center of the galaxy. Otherwise known as Aurigae, an eclipsing binary star rotating around a single point in space. There, the temporal present joins the spatial past and the possible future, and only the most "multiplex" of individuals is able to find their way out again the same way they went in.

In Isaac Asimov's Foundation series, Asimov originally placed the headquarters of the Empire, Trantor, at the dead center of the galaxy. Later, when astronomers gained more knowledge about the center of the galaxy, Asimov amended this to say that Trantor was as close to the galactic center as human habitability allowed.

The home of God!

Ironically, a 1975 Star Trek galactic atlas accurately describes the center of the galaxy as being Sagittarius-A, the supermassive black hole — only one year after astronomers discovered the existence of Sagittarius-A. So Trek lore was actually super cutting edge and highly accurate about the center of our galaxy... until some 14 years later, when Shatner directed Star Trek V: The Final Frontier. Ha. So now, according to Trek, the center of the galaxy contains the mythical planet Sha Ka Ree, said to be the homeworld of God. Except, of course, that it's all a scam. Or something.

The heart of our "Great Mother":

According to the New Age spiritual book 2012 and the Galactic Center, in a couple of years our planet will align with the center of the galaxy for the first time in 26,000 years. And this will allow ordinary humans to experience the kind of heightened awareness usually only reserved for shamans and sages and stuff. Author Christine Page "explains that, as the source of all creation, our galaxy is the Great Mother and its center, her heart. Auspiciously aligning Earth with the heart of the Great Mother, the Galactic Alignment heralds a rebirth of the divine feminine qualities of the Triple Goddess—intuition, emotional creativity, and renewal." It makes total sense.

An alien race who live in the inhospitable galactic core because they don't like other races:

In Greg Egan's Incandescence, almost nobody can go into the "white hot" core of the galaxy. But there's a race living there, who are so aloof that they don't want to talk to any other races. And they are called... the Aloof. From the book's blurb:

The Amalgam spans the nearly entire galaxy, and is composed of innumerable beings from a wild variety of races, some human or near it, some entirely other. The one place that they cannot go is the bulge, the bright, hot center of the galaxy. There dwell the Aloof, who for millions of years have deflected any and all attempts to communicate with or visit them.

Our own ancestors, or older races:

In Fleet Of Worlds by Larry Niven and Edward M. Lerner, the galactic core explodes, sterilizing all of the planets towards the center. The Fleet manages to escape quickly enough to reach a point where the radiation wavefront dissipates, and then the colonists turn back towards the galactic center, where they believe their ancestors, or the oldest races in the galaxy, somehow remain. The galactic center, write Niven and Lerner, is "where myriads of now-sterilized planets lay fallow."

The aftermath from a superweapon.

The science fiction anime series Aim For The Top! Gunbuster does say there's a black hole at the center of the galaxy — but it's the result of the Buster Machine III, aka the Black Hole Bomb, which punched a ginormous hole through the center of the Milky Way Galaxy, creating an incredibly supermassive black hole.

In the 1973 book The Infernoby astronomer Fred Hoyle and his son George, the center of the galaxy goes supernova. And scientists who build a new radio telescope realize that the cosmic rays from the explosion will reach Earth in just two weeks. Only the Scottish survive. No, seriously. The only place that's safe from the radioactive winter that follows the explosion of the galactic core is Scotland. Because haggis.